1. Field of the Invention
The invention relates to a process for preparation of 1,1-dioxopenicillanoyloxymethyl 6-beta-aminopenicillanate by deacylation of a compound of the formula ##STR1## and to intermediate imino chlorides and imino (C.sub.1 -C.sub.4)-alkyl ethers.
2. Description of the Prior Art
Penicillanic acid 1,1-dioxide (sulbactam) is known from U.S. Pat. No. 4,234,579 to be an effective beta-lactamase inhibitor and antibacterial agent.
U.S. Pat. No. 4,244,951 and U.S. Pat. No. 4,342,772 disclose bis esters of the formula ##STR2## wherein R.sup.a is H or certain acyl groups of known antibacterial agents. For example, R.sup.a can represent 2-phenylacetyl, 2-phenoxyacetyl, D-2-amino-2-phenylacetyl or D-2-amino-2-(p-hydroxyphenyl)acetyl. Also disclosed are methods for preparing the above compounds wherein R.sup.a is said acyl by acylation of the 6-amino compound of formula (V) where R.sup.a is hydrogen. The latter compound is prepared by coupling the appropriate derivatives of penicillanic acid 1,1-dioxide and 6-protected-aminopenicillanic acid and removal of protecting group from the coupled product of formula (V) where R.sup.a is an amino-protecting group, e.g. benzyloxycarbonyl.
U.S. Pat. No. 3,896,110 discloses a process for preparation of 6-aminopenicillanic acid by reacting a natural penicillin such as Penicillin G or Penicillin V with a phosphorus halide to protect the carboxyl group, reacting this with an acid halide to form the corresponding penicillin imino halide, reacting the imino halide with an alcohol to form an imino ether and subsequent hydrolysis.